Certain restraint systems at front seats in motor vehicles having a three-point seat belt which provide, inter alia, belt tensioners not only at the shoulder-belt portion, but also at the outer anchorage point of the lap-belt portion, are conventional.
Such a double tightening (shoulder tightening and anchor-fitting tightening) is being considered increasingly by automobile manufacturers because of better biomechanical passenger values (chest acceleration, chest deflection) as well as the avoidance of knee contact with the control panel in all vehicle sizes. In this case, the conventional anchor fitting is replaced by a pyrotechnically ignitable anchor-fitting tightener which, in the event of a crash, pulls belt slack out of the lap-belt portion and reduces the pelvis forward travel, thus having a positive influence on the occupant kinematics. The shoulder tightening takes place as usual, however, the shoulder tightener and anchor-fitting tightener should be activated in time-staggered fashion.
The following anchor-fitting tightener concept is known at present, according to which, in principle, a modified buckle retractor is used. The coupling location between the lap belt and the anchor-fitting tightener is situated visibly in the vehicle. The tightener unit is positioned below the door-sill molding.